Field of the Invention
The invention relates to a mounting unit with a mounting part and a welding element and to a method for producing the mounting unit.
The fixing of a mounting part, for example a sheet-metal-like body part to a basic structure of a motor vehicle, frequently takes place by point welding or resistance welding. In particular in automobile construction, mounting parts made of lightweight materials, such as aluminum, are used, for example, for weight saving reasons. If a mix of materials is produced which is not able to be welded, i.e. if the material of the mounting part cannot be welded to the material of the basic structure, the mounting part is provided with one or more welding elements which consist of a material which is compatible in terms of welding technology with the material of the basic structure, for example steel. The welding element is fixed in a through-bore of the mounting part, wherein the latter has a mounting side and an outer side facing away from the latter. If the mounting unit or the mounting part is fixed to a surface of the basic structure, which surface is referred to hereinafter as the mating surface, the mounting side faces said mating surface.
In the case of a mounting unit known from EP 0 967 044 A2, a disk-shaped welding element is provided, said welding element being inserted in the through-bore of the mounting part by a form-locking connection. The form-locking connection is achieved in that the inner side of the welding element, i.e. the end side thereof that faces in the same direction as the mounting side, has an annular collar which protrudes beyond the end side mentioned and is pressed radially outward into an annular recess in the wall of the through-bore. A disadvantage here is that the welding element or a welding element blank, the annular collar of which is not yet deformed in the abovementioned sense, and the mounting part have to be coordinated with each other with respect to the annular recess in the through-bore and in particular with respect to the length of the through-bore and the thickness of the welding element.